Re: [Xen-devel] [PATCH v4 16/16] xen/arm: add SGI handling for GICv3

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Ian,

On 13 June 2014 09:34, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> On Thu, 2014-06-12 at 22:56 +0100, Julien Grall wrote:
>>
>> On 12/06/14 07:53, Vijay Kilari wrote:
>> >     In GICv3 case the sending SGI by guest raises sysreg trap where
>> > as in GICv2 it raises mmio write trap. So these traps lands in respective
>> > vgic driver. ( mmio write trap => vgic-v2.c and sysreg => vgic-v3.c)
>> > These vgic-v{2,3}.c driver calls generic vgic driver to inject SGI to VCPU.
>>
>> What does prevent a malicious buggy gicv2 guest too call the sysreg
>> version? AFAIU nothing, so you will end up to interpret GICv2 data as
>> GICv3 data which will result to a possible security issue.
>
> ICC_SRE_EL2.Enable should gate EL1's access to this register. We should
> certainly set this to the appropriate value corresponding to what we
> expose to the guest. (I haven't looked if this series does not).

Thanks for information. I suspect the current GICv3 driver is not
ready to support
GICv2 guest. Actually this bit is not context switch.

I'm not sure if it's useful to be there in this current series.

In any case, I think we should add a callback in the vgic structure rather than
exposing a function from the GICv3 driver in the ARM common code.

It might be useful to support other GIC driver... and break, without
good reason,
the idea to have a common layer for the vgic implementation.

Regards,

-- 
Julien Grall

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